This invention relates to a process for separating arsenic from antimony and, more specifically, to a process for the treatment of arsenic and antimony-containing oxidic materials for the recovery of arsenic oxides.
Arsenic and antimony occur in arsenic and antimony minerals as such and in combination with ferrous and non-ferrous metal-containing ores and concentrates. Such ores and concentrates are normally treated for the recovery of ferrous and non-ferrous metals by a number of well known processes based on pyro and/or hydrometallurgical techniques. Arsenic and antimony are present in the form of various compounds formed during these processes and are often concentrated in process materials such as residues, slimes, dusts and fumes in the form of a mixture of oxides. Because of low value, these materials have often been impounded and stockpiled. However, various markets for both arsenic and antimony oxides have developed and an incentive now exists to recover the arsenic and antimony in the form of relatively pure trioxides or pentoxides.
Although there are a number of processes known for the recovery of arsenic and anitmony from ores and concentrates and for the production of antimony and arsenic trioxides and pentoxides, there are few or no commercial and economical processes for the separation of arsenic from high antimony-containing materials.
Processes for the oxidation of arsenic trioxide to arsenic pentoxide which may involve electrolysis or the use of oxidizing agents such as chlorine, nitric acid, nitrogen oxides and oxygen, perchlorate, air and iodine, and hydrogen peroxide have been disclosed in the art. However, none of these processes provides a satisfactory and economical method for the recovery of a relatively pure arsenic trioxide and/or pentoxide or forms the basis for an efficient method for the separation of arsenic and antimony.
It has now been discovered that oxidic materials containing arsenic and antimony can be selectively leached to provide a solution containing a portion of the arsenic present in the oxidic materials and containing substantially no antimony, and a solids residue containing substantially all antimony and the remaining portion of the arsenic. It is, therefore, an object of the present invention to provide a process for the separation of arsenic and antimony.
It is another object of the present invention to provide a process for the selective leaching of arsenic from materials containing arsenic and antimony.
It is a further object of the present invention to provide an economical process for the production of arsenic oxides from arsenic and antimony oxides-containing materials.
These and other objects of the invention and the manner in which they can be attained will become apparent from the following description of the process of the invention.